Uplifted marine terraces in Davao Oriental Province, Mindanao Island, Philippines and their implications for large prehistoric offshore earthquakes along the Philippine trench

作者：Ramos Noelynna T^*; Tsutsumi Hiroyuki; Perez Jeffrey S; Bermas Percival P Jr

来源：Journal of Asian Earth Sciences, 2012, 45: 114-125.

DOI：10.1016/j.jseaes.2011.07.028

• Holocene marine terraces
• Coseismic uplift
• Prehistoric earthquakes
• Philippine trench
• Mindanao Island
• Philippines

We conducted systematic mapping of Holocene marine terraces in eastern Mindanao Island, Philippines for the first time. Raised marine platforms along the 80-km-long coastline of eastern Davao Oriental Province are geomorphic evidence of tectonic deformation resulting from the westward subduction of the Philippine Sea plate along the Philippine trench. Holocene coral platforms consist of up to four terrace steps: Ti: 1-5 m, T2: 3-6 m, T3: 6-10 m, and T4: 8-12 m amsl, from the lowest to highest, respectively. Terraces are subhorizontal, exposing cemented coral shingle and eroded coral heads, while terrace risers are 1-3 m high. Radiocarbon ages, 8080-4140 cal yr BP, reveal that erosional surfaces were carved onto the Holocene transgressive reef complex which grew upward until similar to 8000 years ago. The maximum uplift rate is similar to 1.5 mm/yr based on the highest Holocene terrace at <11.4 m amsl. The staircase topography and meter-scale terrace risers infer that at least four large earthquakes have uplifted the coast in the past similar to 8000 years. The deformation pattern of the terraces further suggests that seismic sources are probably located offshore. However, historical earthquakes as large as M-w 7.5 along the Philippine trench were not large enough to produce meter-scale coastal uplift, suggesting that much larger earthquakes occurred in the past. A long-term tectonic uplift rate of similar to 1.3 mm/yr was also estimated based on Late Pleistocene terraces.

• 出版日期2012-2-2